Trigonometry is not about triangles...
...it's about circles.
The hypotenuse is the radius of a unit circle, and the sin and cosine are the height and width of that line (the vertical and horizontal components of that radial line). As the tip of the radius follows the circumference of the circle, those horizontal and vertical components generate the sine and cosine waves at 90 degree phase to each other. Hence trigonometry is really about how circular motion relates to oscillating motion (think pistons and crankshafts); the stuff about triangles is all fine, but misses the bigger picture.
This is also why the Babylonian table of ratios in the tablet are not going to replace Greek trigonometry any time soon, contrary to the assertion of the historian in the video - ratios of triangle sides miss out the actual point of what trigonometry is about.